The studies investigate the neural processes underlying the initiation and guidance of voluntary limb movements. Chronic experiments are performed on cats trained to make precisely controlled tracking responses with forelimb muscles using a compensatory display. The timing and patterns of muscle contraction associated with the initiation and correction of isometric force adjustments and limb displacements are studied. Both visual and vibrissal information can be used by the cat to initiate responses scaled to target variables with short latencies (less than 100 msec). Under isometric conditions, rapid force adjustments can be described by a pulse-step model where an initial pulsatile output governs the initial dF/dt leading to the peak force, while the step specifies the level of the terminal steady state force. Studies in progress will define the interactions between kinematic variables during limb displacements and the role of sensory input in updating ongoing motor outputs. A second group of experiments investigate the role of neurons in the motor cortex and the red nucleus in the initiation and generation of force in visually guided movement. The role of kinesthetic feedback on these neurons will be determined by comparing the relation between neuronal activity and force exerted under isometric and non-isometric conditions.